Adjustable light distribution for active depth sensing systems

ABSTRACT

Aspects of the present disclosure relate to systems and methods for active depth sensing. An example device includes a light projector. The light projector includes a light source to emit light and a diffractive element. The diffractive element is configured to receive the emitted light that is polarized, project a first distribution of light when the received light has a first polarity, and project a second distribution of light when the received light has a second polarity.

RELATED APPLICATIONS

This patent application claims priority to: U.S. provisional patentapplication No. 62/702,748 entitled “ADJUSTABLE LIGHT DIFFRACTION” filedon Jul. 24, 2018, which is assigned to the assignee hereof; U.S.provisional patent application No. 62/702,770 entitled “ADJUSTABLE LIGHTDIFFRACTION” filed on Jul. 24, 2018, which is assigned to the assigneehereof; and U.S. provisional patent application No. 62/702,782 entitled“ADJUSTABLE LIGHT DIFFRACTION” filed on Jul. 24, 2018, which is assignedto the assignee hereof. The disclosure of the prior applications areconsidered part of and are incorporated by reference in this patentapplication.

This patent application is related to the following United Statesutility patent applications: United States patent application entitled“ADJUSTABLE LIGHT DISTRIBUTION FOR ACTIVE DEPTH SENSING SYSTEMS” andfiled on the same day as the present application, and United Statespatent application entitled “ADJUSTABLE LIGHT PROJECTOR FOR FLOODILLUMINATION AND ACTIVE DEPTH SENSING” and filed on the same day as thepresent application. The disclosures of the applications areincorporated by reference in this patent application.

TECHNICAL FIELD

This disclosure relates generally to light projectors for active depthsensing systems, and specifically to adjusting the distribution of lightfrom such projectors.

BACKGROUND

For active depth sensing, a device may include a light projector toproject a distribution of light, for which reflections of thedistribution of light are sensed and measured to determine distances ofobjects in a scene. For example, a device may include a light projectorthat projects a distribution of infrared (IR) light (such as adistribution of IR light points) onto a scene. An active light receivercaptures reflections of the IR light in capturing an image, and thedevice determines depths or distances of objects in the scene based onthe captured reflections.

SUMMARY

This Summary is provided to introduce in a simplified form a selectionof concepts that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tolimit the scope of the claimed subject matter.

Some aspects of the present disclosure relate to an example deviceincluding an adjustable light projector. The light projector includes alight source to emit light and a diffractive element. The diffractiveelement is configured to receive the emitted light that is polarized,project a first distribution of light when the received light has afirst polarity, and project a second distribution of light when thereceived light has a second polarity.

Some further aspects of the present disclosure relate to a method forprojecting an adjustable light projection. An example method includesemitting polarized light by a light source. The example method alsoincludes projecting, by the diffractive element, a first distribution oflight when the received light has a first polarity. The example methodfurther includes projecting, by the diffractive element, a seconddistribution of light when the received light has a second polarity.

Some other aspects of the present disclosure relate to an exampledevice. An example device includes means for emitting polarized light.The example device also includes means for projecting a firstdistribution of light from the light based on the light having a firstpolarity. The example device further includes means for projecting asecond distribution of light from the light based on the light having asecond polarity.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are illustrated by way of example, andnot by way of limitation, in the figures of the accompanying drawingsand in which like reference numerals refer to similar elements.

FIG. 1 is a depiction of an example active depth sensing systemincluding a light projector for projecting a distribution of light.

FIG. 2 is a depiction of an example projector of an active depth sensingsystem.

FIG. 3 is a depiction of another example projector of an active depthsensing system.

FIG. 4 is a depiction of an example device including an active depthsensing light projector and a flood illuminator.

FIG. 5 is a depiction of an example flood illuminator.

FIG. 6 is a block diagram of an example device including an adjustablediffraction projector.

FIG. 7A is a depiction of an example arrangement of multiple diffractiveoptical elements of an adjustable diffraction projector.

FIG. 7B is a depiction of another example arrangement of multiplediffractive optical elements of an adjustable diffraction projector.

FIG. 7C is a depiction of a further example arrangement of multiplediffractive optical elements of an adjustable diffraction projector.

FIG. 7D is a depiction of another example arrangement of multiplediffractive optical elements of an adjustable diffraction projector.

FIG. 7E is a depiction of a further example arrangement of multiplediffractive optical elements of an adjustable diffraction projector.

FIG. 7F is a depiction of another example arrangement of multiplediffractive optical elements of an adjustable diffraction projector.

FIG. 7G is a depiction of a further example arrangement of multiplediffractive optical elements of an adjustable diffraction projector.

FIG. 7H is a depiction of another example arrangement of multiplediffractive optical elements of an adjustable diffraction projector.

FIG. 7I is a depiction of a further example arrangement of multiplediffractive optical elements of an adjustable diffraction projector.

FIG. 8 is a depiction of an example diffractive element including anarrangement of two diffractive optical elements with a refractivematerial between the two diffractive optical elements (DOE).

FIG. 9A is a depiction of two example DOEs with a refractive material inbetween, where a first DOE and the refractive material have the samerefractive index.

FIG. 9B is a depiction of the two example DOEs with the refractivematerial in between in FIG. 9A, where the second DOE and the refractivematerial have the same refractive index.

FIG. 9C is a depiction of two example DOEs with the refractive materialin between, where the uneven surface of the second DOE is oriented awayfrom the refractive material, and the first DOE and the refractivematerial have the same refractive index.

FIG. 9D is a depiction of the two example DOEs with the refractivematerial in between, where the uneven surface of the second DOE isoriented away from the refractive material, and the second DOE and therefractive material have the same refractive index.

FIG. 9E is a depiction of two example DOEs with the refractive materialin between, where the uneven surface of the first DOE is oriented awayfrom the refractive material, and the first DOE and the refractivematerial have the same refractive index.

FIG. 9F is a depiction of the two example DOEs with the refractivematerial in between, where the uneven surface of the first DOE isoriented away from the refractive material, and the second DOE and therefractive material have the same refractive index.

FIG. 10 is a depiction of example polarization orientations including afirst polarity and a second polarity ninety degrees from each other.

FIG. 11 is a depiction of example first and second distributionscombined for a combined distribution.

FIG. 12 is a depiction of an example distribution and an example floodillumination combined for a projector.

FIG. 13A is a depiction of an example projector configured to apply anelectricity to the liquid crystal of the diffractive element of theprojector for generating a projection.

FIG. 13B is another depiction of the example projector in FIG. 13A witha different example location of the conductive material for applyingelectricity to the liquid crystal.

FIG. 13C is another depiction of the example projector in FIG. 13A witha different example location of the conductive material for applyingelectricity to the liquid crystal.

FIG. 14 is a depiction of an example projector configured to adjust thepolarity of the light passing through a diffractive element of theprojector for generating a projection.

FIG. 15 is a depiction of example adjustments to the polarity of thelight by adjusting the polarity rotator.

FIG. 16A is a depiction of example projections based on the polarity oflight passing through the diffractive element.

FIG. 16B is a depiction of further example projections based on thepolarity of light passing through the diffractive element.

FIG. 17 is an illustrative flow chart depicting an example operation foradjusting the distribution of light to be projected by a projector.

FIG. 18 is an illustrative flow chart depicting an example operation foradjusting the distribution of light by a light projector.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to active light projectors andflood illuminators, and include a light projector with an adjustablediffraction of the projected light.

An active depth sensing system may transmit light in a predefineddistribution of points (or another suitable shape of focused light). Thepoints of light may be projected on to a scene, and the reflections ofthe points of light may be received by the active depth sensing system.Depths of objects in a scene may be determined by comparing the patternof the received light and the pattern of the transmitted light. Incomparing the patterns, a portion of the predefined distribution for thetransmitted light may be identified in the received light. In thepresent disclosure, an active depth sensing system that projects adistribution of light (such as a distribution of light points or othershapes) is referred to as a structured light system (with a structuredlight projector).

The light distribution emitted by a structured light projector does notchange. Denser distributions of light (such as additional light pointsor more instances of focused light in an area than for sparserdistributions of light) may result in a higher resolution of a depth mapor a greater number of depths that may be determined. However, theintensity of individual light points are lower for denser distributionsthan for sparser distributions where the overall intensity is similarbetween the distribution. As a result, interference may causeidentifying reflections of a denser distribution of light more difficultthan for sparser distributions of light. For example, a structured lightprojector may project IR light (such as near infrared (NIR) light) witha 905 nm or 940 nm wavelength (or other suitable wavelength). Astructured light receiver may receive reflections of the IR light aswell as sunlight and other ambient light. Ambient light may causeinterference of the IR light points. As a result, brightly lit scenes(such as outdoor scenes in daylight) may cause more interference thandarker scenes (such as indoor scenes or nighttime) because of theadditional ambient light being captured by the structured lightreceiver.

A structured light system may overcome interference by increasing thelight intensity. For example, the structured light projector may usemore power to increase the intensity of each light point. However, toensure eye safety and compliance with any regulations on lighttransmission, the overall intensity of light in an area of theprojection may be restricted. In this manner, the number of points orinstances of light in the area affects the maximum intensity of eachpoint or instance of light. As a result, each light point in a sparserdistribution may have a higher maximum intensity than each light pointin a denser distribution. Thus, a sparser distribution may be moresuitable for daylight scenes (with more interference), and a denserdistribution may be more suitable for indoor or nighttime scenes (withless interference).

However, many devices use the same structured light system in differenttypes of lighting (with different amounts of interference). For example,a smartphone may include an active depth sensing system for faceidentification, and the smartphone may be used indoors and outdoors. Ifthe light distribution for the structured light projector is fixed, thedevice would need to include more than one structured light projector toproject distributions of light at different densities (and thusdifferent intensities for each of the light instances in the lightdistributions). In some aspects of the present disclosure, a lightprojector may be configured to adjust the density of the lightdistribution.

Many devices also include a flood illuminator. A flood illuminator mayproject a diffuse light onto a scene so that enough light exists in thescene for an image sensor to capture one or more images of the scene. Inone example, a device that performs face identification may need tofirst determine if a face to be identified exists in the scene. Thedevice may include a flood illuminator to project IR light onto a sceneso that an IR sensor may capture the scene and the device may determinefrom the capture if a face exists in the scene. If a face is determinedto exist in the scene, the device may then use an active depth sensingsystem for face identification. If a light projector has a fixeddistribution or refraction of light, a device including a floodilluminator and a structured light projector therefore is required toinclude at least two light projectors (such as two IR projectors). Insome aspects of the present disclosure, a light projector may beadjustable to project diffuse light for flood illumination (such as forface detection) or project a distribution of light for active depthsensing (such as for face identification).

If a light projector is configured to adjust the density of thestructured light projection or is configured to switch between floodillumination and active depth sensing, a device may include fewer lightprojectors, thus saving device space and requiring fewer devicecomponents.

In the following description, numerous specific details are set forth,such as examples of specific components, circuits, and processes toprovide a thorough understanding of the present disclosure. The term“coupled” as used herein means connected directly to or connectedthrough one or more intervening components or circuits. Also, in thefollowing description and for purposes of explanation, specificnomenclature is set forth to provide a thorough understanding of thepresent disclosure. However, it will be apparent to one skilled in theart that these specific details may not be required to practice theteachings disclosed herein. In other instances, well-known circuits anddevices are shown in block diagram form to avoid obscuring teachings ofthe present disclosure. Some portions of the detailed descriptions whichfollow are presented in terms of procedures, logic blocks, processes,and other symbolic representations of operations on data bits within acomputer memory. In the present disclosure, a procedure, logic block,process, or the like, is conceived to be a self-consistent sequence ofsteps or instructions leading to a desired result. The steps are thoserequiring physical manipulations of physical quantities. Usually,although not necessarily, these quantities take the form of electricalor magnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated in a computer system.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present application,discussions utilizing the terms such as “accessing,” “receiving,”“sending,” “using,” “selecting,” “determining,” “normalizing,”“multiplying,” “averaging,” “monitoring,” “comparing,” “applying,”“updating,” “measuring,” “deriving,” “settling” or the like, refer tothe actions and processes of a computer system, or similar electroniccomputing device, that manipulates and transforms data represented asphysical (electronic) quantities within the computer system's registersand memories into other data similarly represented as physicalquantities within the computer system memories or registers or othersuch information storage, transmission or display devices.

In the figures, a single block may be described as performing a functionor functions; however, in actual practice, the function or functionsperformed by that block may be performed in a single component or acrossmultiple components, and/or may be performed using hardware, usingsoftware, or using a combination of hardware and software. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps aredescribed below generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure. Also, the example devices may includecomponents other than those shown, including well-known components suchas a processor, memory and the like.

Aspects of the present disclosure are applicable to any suitableelectronic device (such as security systems, smartphones, tablets,laptop computers, vehicles, drones, or other devices) including orcoupled to one or more active depth sensing systems. While describedbelow with respect to a device having or coupled to one light projector,aspects of the present disclosure are applicable to devices having anynumber of light projectors, and are therefore not limited to specificdevices.

The term “device” is not limited to one or a specific number of physicalobjects (such as one smartphone, one controller, one processing systemand so on). As used herein, a device may be any electronic device withone or more parts that may implement at least some portions of thisdisclosure. While the below description and examples use the term“device” to describe various aspects of this disclosure, the term“device” is not limited to a specific configuration, type, or number ofobjects. Additionally, the term “system” is not limited to multiplecomponents or specific embodiments. For example, a system may beimplemented on one or more printed circuit boards or other substrates,and may have movable or static components. While the below descriptionand examples use the term “system” to describe various aspects of thisdisclosure, the term “system” is not limited to a specificconfiguration, type, or number of objects.

FIG. 1 is a depiction of an example active depth sensing system 100. Theactive depth sensing system 100 (which herein also may be called astructured light system) may be used to generate a depth map (notpictured) of a scene 106. For example, the scene 106 may include a face,and the active depth sensing system 100 may be used for identifying orauthenticating the face. The active depth sensing system 100 may includea projector 102 and a receiver 108. The projector 102 may be referred toas a “transmitter,” “projector,” “emitter,” and so on, and should not belimited to a specific transmission component. Throughout the followingdisclosure, the terms projector and transmitter may be usedinterchangeably. The receiver 108 may be referred to as a “detector,”“sensor,” “sensing element,” “photodetector,” and so on, and should notbe limited to a specific receiving component.

While the disclosure refers to the distribution as a light distribution,any suitable wireless signals at other frequencies may be used (such asradio frequency waves, sound waves, etc.). Further, while the disclosurerefers to the distribution as including a plurality of light points, thelight may be focused into any suitable size and dimensions. For example,the light may be projected in lines, squares, or any other suitabledimension. In addition, the disclosure may refer to the distribution asa codeword distribution, where a defined portion of the distribution(such as a predefined patch of light points) is referred to as acodeword. If the distribution of the light points is known, thecodewords of the distribution may be known. However, the distributionmay be organized in any way, and the present disclosure should not belimited to a specific type of distribution or type of wireless signal.

The transmitter 102 may be configured to project or transmit adistribution 104 of light points onto the scene 106. The white circlesin the distribution 104 may indicate where no light is projected for apossible point location, and the black circles in the distribution 104may indicate where light is projected for a possible point location. Insome example implementations, the transmitter 102 may include one ormore light sources 124 (such as one or more lasers), a lens 126, and alight modulator 128. The transmitter 102 also may include an aperture122 from which the transmitted light escapes the transmitter 102. Insome implementations, the transmitter 102 may further include adiffractive optical element (DOE) to diffract the emissions from one ormore light sources 124 into additional emissions. In some aspects, thelight modulator 128 (to adjust the intensity of the emission) maycomprise a DOE. In projecting the distribution 104 of light points ontothe scene 106, the transmitter 102 may transmit one or more lasers fromthe light source 124 through the lens 126 (and/or through a DOE or lightmodulator 128) and onto the scene 106. The transmitter 102 may bepositioned on the same reference plane as the receiver 108, and thetransmitter 102 and the receiver 108 may be separated by a distancecalled the baseline (112).

In some example implementations, the light projected by the transmitter102 may be IR light. IR light may include portions of the visible lightspectrum and/or portions of the light spectrum that is not visible tothe naked eye. In one example, IR light may include near infrared (NIR)light, which may or may not include light within the visible lightspectrum, and/or IR light (such as far infrared (FIR) light) which isoutside the visible light spectrum. The term IR light should not belimited to light having a specific wavelength in or near the wavelengthrange of IR light. Further, IR light is provided as an example emissionfrom the transmitter. In the following description, other suitablewavelengths of light may be used. For example, light in portions of thevisible light spectrum outside the IR light wavelength range orultraviolet light. Alternatively, other signals with differentwavelengths may be used, such as microwaves, radio frequency signals,and other suitable signals.

The scene 106 may include objects at different depths from thestructured light system (such as from the transmitter 102 and thereceiver 108). For example, objects 106A and 106B in the scene 106 maybe at different depths. The receiver 108 may be configured to receive,from the scene 106, reflections 110 of the transmitted distribution 104of light points. To receive the reflections 110, the receiver 108 maycapture an image. When capturing the image, the receiver 108 may receivethe reflections 110, as well as (i) other reflections of thedistribution 104 of light points from other portions of the scene 106 atdifferent depths and (ii) ambient light. Noise may also exist in thecaptured image.

In some example implementations, the receiver 108 may include a lens 130to focus or direct the received light (including the reflections 110from the objects 106A and 106B) on to the sensor 132 of the receiver108. The receiver 108 also may include an aperture 120. Assuming for theexample that only the reflections 110 are received, depths of theobjects 106A and 106B may be determined based on the baseline 112,displacement and distortion of the light distribution 104 (such as incodewords) in the reflections 110, and intensities of the reflections110. For example, the distance 134 along the sensor 132 from location116 to the center 114 may be used in determining a depth of the object106B in the scene 106. Similarly, the distance 136 along the sensor 132from location 118 to the center 114 may be used in determining a depthof the object 106A in the scene 106. The distance along the sensor 132may be measured in terms of number of pixels of the sensor 132 or adistance (such as millimeters).

In some example implementations, the sensor 132 may include an array ofphotodiodes (such as avalanche photodiodes) for capturing an image. Tocapture the image, each photodiode in the array may capture the lightthat hits the photodiode and may provide a value indicating theintensity of the light (a capture value). The image therefore may be thecapture values provided by the array of photodiodes.

In addition or alternative to the sensor 132 including an array ofphotodiodes, the sensor 132 may include a complementary metal-oxidesemiconductor (CMOS) sensor. To capture the image by a photosensitiveCMOS sensor, each pixel of the sensor may capture the light that hitsthe pixel and may provide a value indicating the intensity of the light.In some example implementations, an array of photodiodes may be coupledto the CMOS sensor. In this manner, the electrical impulses generated bythe array of photodiodes may trigger the corresponding pixels of theCMOS sensor to provide capture values.

The sensor 132 may include at least a number of pixels equal to thenumber of possible light points in the distribution 104. For example,the array of photodiodes or the CMOS sensor may include a number ofphotodiodes or a number of pixels, respectively, corresponding to thenumber of possible light points in the distribution 104. The sensor 132logically may be divided into groups of pixels or photodiodes (such as4×4 groups) that correspond to a size of a bit of a codeword. The groupof pixels or photodiodes also may be referred to as a bit, and theportion of the captured image from a bit of the sensor 132 also may bereferred to as a bit. In some example implementations, the sensor 132may include the same number of bits as the distribution 104.

If the light source 124 transmits IR light (such as NIR light at awavelength of, e.g., 940 nm), the sensor 132 may be an IR sensor toreceive the reflections of the NIR light. The sensor 132 also may beconfigured to capture an image using a flood illuminator (notillustrated).

As illustrated, the distance 134 (corresponding to the reflections 110from the object 106B) is less than the distance 136 (corresponding tothe reflections 110 from the object 106A). Using triangulation based onthe baseline 112 and the distances 134 and 136, the differing depths ofobjects 106A and 106B in the scene 106 may be determined in generating adepth map of the scene 106. Determining the depths may further includedetermining a displacement or a distortion of the distribution 104 inthe reflections 110.

Although a number of separate components are illustrated in FIG. 1, oneor more of the components may be implemented together or includeadditional functionality. All described components may not be requiredfor an active depth sensing system 100, or the functionality ofcomponents may be separated into separate components. Additionalcomponents not illustrated also may exist. For example, the receiver 108may include a bandpass filter to allow signals having a determined rangeof wavelengths to pass onto the sensor 132 (thus filtering out signalswith a wavelength outside of the range). In this manner, some incidentalsignals (such as ambient light) may be prevented from interfering withthe captures by the sensor 132. The range of the bandpass filter may becentered at the transmission wavelength for the transmitter 102. Forexample, if the transmitter 102 is configured to transmit NIR light witha wavelength of 940 nm, the receiver 108 may include a bandpass filterconfigured to allow NIR light having wavelengths within a range of,e.g., 920 nm to 960 nm. Therefore, the examples described regarding FIG.1 is for illustrative purposes, and the present disclosure should not belimited to the example active depth sensing system 100.

For a light projector (such as the transmitter 102), the light sourcemay be any suitable light source. In some example implementations, thelight source 124 may include one or more distributed feedback (DFB)lasers. In some other example implementations, the light source 124 mayinclude one or more vertical-cavity surface-emitting lasers (VCSELs).

A DOE is a material situated in the projection path of the light fromthe light source. The DOE may be configured to split a light point intomultiple light points. For example, the material of the DOE may be atranslucent or a transparent polymer with a known refractive index. Thesurface of the DOE may include peaks and valleys (varying the depth ofthe DOE) so that a light point splits into multiple light points whenthe light passes through the DOE. For example, the DOE may be configuredto receive one or more lights points from one or more lasers and projectan intended distribution with a greater number of light points thanemitted by the one or more lasers. While the Figures may illustrate thedepth of a DOE changing along only one axis of the DOE, the Figures areonly to assist in describing aspects of the disclosure. The peaks andvalleys of the surface of the DOE may be located at any portion of thesurface of the DOE and cause any suitable change in the depth ofportions of the DOE, and the present disclosure should not be limited toa specific surface configuration for a DOE.

If the light source 124 includes an array of lasers (such as a VCSELarray), a portion of the distribution of light points may be projectedby the array. A DOE may be used to replicate the portion in projectingthe distribution of light points. For example, the DOE may split theprojection from the array into multiple instances, and the pattern ofthe projection may be a repetition of the projection from the array. Insome example implementations, the DOE may be configured to repeat theprojection vertically, horizontally, or at an angle between vertical andhorizontal relative to the projection. The repeated instances may beoverlapping, non-overlapping, or any suitable configuration. While theexamples describe a DOE configured to split the projection from thearray and stack the instances above and below one another, the presentdisclosure should not be limited to a specific type of DOE configurationand repetition of the projection.

FIG. 2 is a depiction of an example projector 200 of an active depthsensing system. The projector 200 may be an example implementation ofthe transmitter 102 in FIG. 1. The example projector 200 may include alaser 202 that is configured to emit a light 204 toward a lens 206. Thelens 206 may contain one or more lens elements to direct the light 204,and the lens 206 is shown only for illustrative purposes. An examplelaser 202 is a DFB laser, which may emit polarized light toward the lens206. Another example laser 202 is a VCSEL, which may emit unpolarizedlight 204 toward the lens 206. The lens 206 may direct the light 204toward the DOE 208. The DOE 208 may have a first refractive index, and asurface 210 of the DOE 208 may be configured for the DOE 208 to projectthe distribution of light points 212 from the light 204. Some exampleimplementations of fabricating a DOE (such as DOE 208) includedepositing a polymer layer or dielectric layer on a glass (or otherwisetransparent) substrate. The deposited layer may have a desiredrefractive index and may be deposited with different depths, thusproviding the desired characteristics for the DOE.

FIG. 3 is a depiction of another example projector 300 of an activedepth sensing system. The projector 300 may be similar to the projector200 in FIG. 2, except the projector 300 includes a plurality of lasers(such as a laser array 302) instead of one laser 202. The laser array302 may emit a plurality of light points 304. The light points 304 maybe in a pattern, with each point indicating a light emitted by one ofthe lasers in the laser array 302. The lens 306 may direct the lightpoints 304 to the DOE 308 to project the distribution of light points304 onto the scene. The DOE 308 may have a first refractive index, andthe surface 310 of the DOE 308 may be configured for the DOE 308 toreplicate the light points 304 into multiple instances of light points314. The distribution of light points 312 therefore may include themultiple instances of light points 314. Each instance may be of thepattern of light points 304.

The DOE 308 may be configured to split the light points 304 intoinstances 314 and vertically stack the instances 314 in projecting thedistribution 312. For example, the DOE 308 may include horizontal ridgesfor splitting the light points 304 vertically. While the exampleprojector 300 is illustrated as vertically splitting and stacking thelight points 304, the DOE 308 may be configured to divide the lightpoints 304 and arrange the instances in any suitable manner. Forexample, the instances may be overlapping or spaced apart, stackedhorizontally, tiled, or arranged in another suitable shape or order. Thepresent disclosure should not be limited to a specific configuration forthe DOE 308.

Referring to FIG. 2 and FIG. 3, the distribution 212 and thedistribution 312 are unchanging for a fixed DOE 208 and DOE 308,respectively. However, the DOE 208 in FIG. 2 or the DOE 308 in FIG. 3may be replaced with a configurable diffractive element that may beconfigured to adjust the distribution 212 or the distribution 312,respectively. For example, a configurable diffractive element may beconfigured to decrease or increase the number of light points in thedistribution.

In addition to active depth sensing, a device may be configured toprovide flood illumination. FIG. 4 is a depiction of an example device400 including an active depth sensing light projector 402 and a floodilluminator 404. The device 400 further may include an IR sensor 406 tocapture an image based on the reflections of light from the active depthsensing light projector 402 or the flood illuminator 404 (with theprojector 402 and the illuminator 404 projecting IR light). Thestructured light projector 402 and the IR sensor 406 may be separated bya baseline 408. An example device 400 may be a smartphone, with anearpiece 410 and a microphone 412 for conducting phone calls or otherwireless communications. A smartphone also may include a display 414with or without a notch including the projectors 402, illuminator 404,and the IR sensor 406.

A flood illuminator 404 may project a diffuse IR light onto a scene forthe IR sensor 406 to capture an image based on reflections of thediffuse IR light. FIG. 5 is a depiction of an example flood illuminator500. The flood illuminator 500 may be an example implementation of theflood illuminator 404 in FIG. 4. The flood illuminator 500 may include aLaser 502 (such as a DFB laser or a VCSEL) configured to emit light 504toward a lens 506. The lens 506 may direct the light 504 to a diffusionelement 508. The diffusion element 508 may have a refractive index andinclude a surface 510 configured to adjust the light passing through thediffusion element 508 such that the light projected from the diffusionelement 508 is a diffuse light 512. An example diffusion element 508 isa Fresnel lens. However, any suitable diffusion element 508 may be usedfor diffusing the light 504.

Referring back to FIG. 4, a device 400 including an active depth sensinglight projector 402 and a flood illuminator 404 would require at leasttwo projectors. In some example implementations, the diffusion element508 in FIG. 5 or the DOE 208 in FIG. 2 may be replaced with aconfigurable element so that a projector may be configured to project adiffuse light (when operating as a flood illuminator) and to project adistribution of light (when operating as a light projector for activedepth sensing). In this manner, a device may include one projector forboth flood illumination and active depth sensing. For example, theprojector 402 of the device 400 in FIG. 4 may be configured to performflood illumination and light projection for active depth sensing, andthe device 400 therefore may not include the separate flood illuminator404.

If a device includes a projector that is configurable to adjust thedensity of a light distribution for different operating modes, and/or ifthe device includes a projector that is configurable to switch betweenflood illumination and light projection for active depth sensing fordifferent operating modes, the device may control configuring andoperating the projector for the different operating modes. FIG. 6 is ablock diagram of an example device 600 for configuring a transmitter 601for active depth sensing (which may project different densitydistributions of light) and/or flood illumination. In some otherexamples, a transmitter may be separate from and coupled to the device600.

The example device 600 may include or be coupled to a transmitter 601and a receiver 602 separated from the transmitter 601 by a baseline 603.The receiver 602 may be an IR sensor configured to capture images, andthe transmitter 601 may be a projector configured to project adistribution of light and/or a diffuse light. The density of thedistribution of light from the transmitter 601 may be adjustable.

The example device 600 also may include a processor 604, a memory 606storing instructions 608, and a light controller 610 (which may includeone or more signal processors 612). The device 600 may optionallyinclude (or be coupled to) a display 614 and a number of input/output(I/O) components 616. The device 600 may include additional features orcomponents not shown. For example, a wireless interface, which mayinclude a number of transceivers and a baseband processor, may beincluded for a wireless communication device to perform wirelesscommunications. In another example, the device 600 may include one ormore cameras (such as a contact image sensor (CIS) camera or othersuitable camera for capturing images using visible light). Thetransmitter 601 and the receiver 602 may be part of an active depthsensing system (such as the system 100 in FIG. 1) controlled by thelight controller 610 and/or the processor 604. The transmitter 601 andthe receiver 602 additionally may be a flood illumination and capturesystem. The device 600 may include or be coupled to additional lightprojectors (or flood illuminators) or may include a differentconfiguration for the light projectors. The device 600 also may includeor be coupled to additional receivers (not shown) for capturing multipleimages of a scene. The disclosure should not be limited to any specificexamples or illustrations, including the example device 600.

The memory 606 may be a non-transient or non-transitory computerreadable medium storing computer-executable instructions 608 to performall or a portion of one or more operations described in this disclosure.If the light distribution projected by the transmitter 601 is dividedinto codewords, the memory 606 optionally may store a library ofcodewords 609 for the codeword distribution of light. The library ofcodewords 609 may indicate what codewords exist in the distribution andthe relative location between the codewords in the distribution. Thedevice 600 also may include a power supply 618, which may be coupled toor integrated into the device 600.

The processor 604 may be one or more suitable processors capable ofexecuting scripts or instructions of one or more software programs (suchas instructions 608 stored within the memory 606). In some aspects, theprocessor 604 may be one or more general purpose processors that executeinstructions 608 to cause the device 600 to perform any number offunctions or operations. In additional or alternative aspects, theprocessor 604 may include integrated circuits or other hardware toperform functions or operations without the use of software. While shownto be coupled to each other via the processor 604 in the example of FIG.6, the processor 604, the memory 606, the light controller 610, theoptional display 614, and the optional I/O components 616 may be coupledto one another in various arrangements. For example, the processor 604,the memory 606, the light controller 610, the optional display 614,and/or the optional I/O components 616 may be coupled to each other viaone or more local buses (not shown for simplicity).

The display 614 may be any suitable display or screen allowing for userinteraction and/or to present items (such as a depth map, a previewimage of the scene, a lock screen, etc.) for viewing by a user. In someaspects, the display 614 may be a touch-sensitive display. The I/Ocomponents 616 may be or include any suitable mechanism, interface, ordevice to receive input (such as commands) from the user and to provideoutput to the user. For example, the I/O components 616 may include (butare not limited to) a graphical user interface, keyboard, mouse,microphone and speakers, squeezable bezel or border of the device 600,physical buttons located on device 600, and so on. The display 614and/or the I/O components 616 may provide a preview image or depth mapof the scene to a user and/or receive a user input for adjusting one ormore settings of the device 600 (such as for adjusting the density ofthe distribution projected by the transmitter 601, switching theprojection from diffuse light to a distribution of light points by thetransmitter 601, etc.).

The light controller 610 may include a signal processor 612, which maybe one or more processors to configure the transmitter 601 and processimages captured by the receiver 602. In some aspects, the signalprocessor 612 may execute instructions from a memory (such asinstructions 608 from the memory 606 or instructions stored in aseparate memory coupled to the signal processor 612). In other aspects,the signal processor 612 may include specific hardware for operation.The signal processor 612 may alternatively or additionally include acombination of specific hardware and the ability to execute softwareinstructions. While the following examples may be described in relationto the device 600, any suitable device or configuration of devicecomponents may be used, and the present disclosure should not be limitedby a specific device configuration.

For the projector (such as the transmitter 601 in FIG. 6), thediffractive element may be configured so that the light projection isadjustable. To be configurable to adjust the light projection, thediffractive element may include a plurality of DOEs. In some exampleimplementations, a diffusion element (for flood illumination) may be oneof the DOEs. In some other example implementations, two or more DOEs maycause the final light projection to have different light distributionsfor active depth sensing. In some examples, the multiple DOEs arepositionally fixed (do not move) within the projector or relative to thelight source, and other projector components may be adjusted whenadjusting the light projection. While the following examples describetwo DOEs for the projector, any number of DOEs may be used, and thepresent disclosure should not be limited to a projector including twoDOEs.

FIG. 7A is a depiction of an example arrangement 700 of two DOEs for aprojector. The DOEs may include a DOE for distributed light projectionand a diffusion element/DOE for flood illumination. The DOEs may bealigned in the projection path of light from a light source of theprojector, and the uneven surfaces of the DOEs (indicated by the jaggedlines) may be oriented in the same direction (as illustrated). FIG. 7Bis a depiction of another example arrangement 710 of two DOEs for aprojector. The arrangement 710 is similar to the arrangement 700 in FIG.7A, except that the uneven surfaces of the DOEs may be oriented towardeach other.

FIG. 7C is a depiction of a further example arrangement 720 of two DOEsfor a projector. The DOEs may include two DOEs for differentdistributions of light projection (for active depth sensing). The unevensurfaces of the DOEs may be the same. Alternatively, the uneven surfacesof the DOEs may be different. In one example, the uneven surfaces of theDOEs may be the same, except the surface of one DOE may be spatiallyshifted so that the similar surfaces do not align on the projection pathof the light. In another example, the uneven surfaces may be different(such as a different number of peaks and valleys and thus a differingnumber and/or size of depths of the DOEs). Similar to FIG. 7A, theuneven surfaces of the DOEs may be oriented in the same direction. FIG.7D is a depiction of another example arrangement 730 of two DOEs for aprojector. The arrangement 730 is similar to the arrangement 720 in FIG.7C, except that the uneven surfaces of the DOEs may be oriented towardeach other.

Referring back to FIG. 7A and FIG. 7B, the diffusion element isillustrated as after a DOE for distributed light projection (with lightpassing from left to right through the elements). In some alternativeimplementations, the diffusion element may be before the distributedlight projection DOE along the light path. FIG. 7E is a depiction ofanother example arrangement 740 of two DOEs for a projector. Thearrangement 740 is similar to the arrangement 700 in FIG. 7A, exceptthat the order of the DOEs is switched. FIG. 7F is a depiction of afurther example arrangement 750 of two DOEs for a projector. Thearrangement 750 is similar to the arrangement 710 in FIG. 7B, exceptthat the order of the DOEs is switched.

For FIGS. 7A-7F, the uneven surface of the first DOE (e.g., the left DOEfor a direction of the light from left to right) is oriented toward thesubsequent (right) DOE. In some other example implementations, theuneven surface of the first DOE may be oriented toward the light source(away from the subsequent DOE). FIG. 7G-FIG. 7I are depictions offurther example arrangements 760-780 of two DOEs for a projector. Thearrangements 760, 770, and 780 in FIG. 7G-FIG. 7I are similar to thearrangements 710, 730, and 750 in FIG. 7B, FIG. 7D, and FIG. 7F,respectively, except that the first DOE is oriented in the oppositedirection (with the uneven surface oriented toward a light sourceinstead of the other DOE).

For multiple DOEs in a projector, the refractive index of each DOE maybe different from one another. For example, the first DOE in FIGS. 7A-7Imay have a first refractive index, and the second DOE may have a secondrefractive index different than the first refractive index. For example,the refractive indexes may be different if they are significantlydifferent (e.g., the difference is greater than a threshold). In thismanner, the difference in refraction between the DOEs may be perceptibleor substantial for operating purposes. In some example implementations,DOEs may be spaced apart from each other. While the following examplesdescribe two DOEs having the uneven surfaces oriented toward each other,other orientations of the DOEs may be used (such as any of theorientations in FIGS. 7A-7I), and the present disclosure should not belimited to the following examples in orienting the DOEs.

The space between the two DOEs may be filled with a transparent ortranslucent material having different refractive indexes than the twoDOEs. For example, the differences between the refractive index for thematerial and the two DOEs are greater than a threshold (and thedifferences may be perceptible or substantial for operating purposes).In some example implementations, the refractive index may be switchablefor the material. Additionally or alternatively, the refractive indexfor the material may differ for different polarities of light passingthrough the material.

FIG. 8 is a depiction of a diffractive element 800 including two DOEs802 and 804 with a refractive material 806 in between. The DOEs 802 and804 may be spaced apart by spacers 808. Alternatively, the refractivematerial 806 may be sufficient to separate the DOEs 802 and 804 (such ashaving a sufficient structure or inelasticity). In some exampleimplementations, the refractive material 806 may have an averagerefractive index different (e.g., the differences being greater than athreshold) than the refractive indexes for the DOEs 802 and 804. If therefractive indexes are different for the first DOE 802, the second DOE804, and the refractive material 806 (e.g., the differences beinggreater than a threshold), light passing through the DOEs 802 and 804and the refractive material 806 may be affected by both DOEs 802 and804. For example, if the first DOE 802 splits a light from a laser intoa first distribution of light points, the first distribution of lightpoints may pass through the refractive material 806 to the second DOE804. If the second DOE 804 splits a light into a second distribution oflight points, each light point of the first distribution of light pointsmay be split into a separate second distribution of light points. Inthis manner, the number of light points of the first distribution fromthe first DOE 802 may be increased by the second DOE 804.

When a light point is divided into multiple light points, the energy isdivided among the multiple light points. As a result, the intensity ofeach of the resulting light points is less than the intensity of theoriginal light point. In this manner, the distribution of, e.g., pointsof light may be denser without the intensity of the light for a portionof the distribution increasing (thus allowing an overall maximumintensity of the projected light to remain below an overall maximumintensity while increasing the density of light points for the projectedlight).

If the refractive index of the refractive material 806 is the same as afirst refractive index of the first DOE 802 or a second refractive indexof the second DOE 804, light may not be affected by the DOE with thesame refractive index as the refractive material 806. Same refractiveindexes may be similar refractive indexes, such as the differencebetween the refractive indexes being less than a threshold. For example,refractive indexes may be the same for two refractive indexes whosedifference is less than the threshold and different for two refractiveindexes whose difference is greater than the threshold. The followingdescription uses the terms “different,” “same,” and “similar.” However,“different” may be a difference greater than an absolute difference(e.g., the differences being greater than a determined threshold), and“same” or “similar” may not be absolutely the same (e.g., thedifferences may be less than a determined threshold or the differencesare not perceptible for operation of the device). The present disclosureshould not be limited to a specific difference or similarity through useof the terms.

FIG. 9A is a depiction 900 of two DOEs 902 and 904 with a refractivematerial 906 in between. The refractive index of the first DOE 902 andthe refractive index of the refractive material 906 may be the same(e.g., the differences being less than a threshold). In this manner, thesurface 908 may seem to be non-existent to light passing through thefirst DOE 902 and the refractive material 906. As a result, thedistribution of light passing through the diffractive element is onlyaffected by the second DOE 904 with the surface 910. FIG. 9B is adepiction 950 of the two DOEs 902 and 904 with the refractive material906 in between. The refractive index of the second DOE 904 and therefractive index of the material 906 may be the same (e.g., thedifferences being less than a threshold). In this manner, the surface910 may seem to be non-existent to light passing through the material906 and the second DOE 904. As a result, the distribution of lightpassing through the diffractive element is only affected by the firstDOE 904 with the surface 908.

In some other example orientations for the DOE 902 and the DOE 904(which either may be for projecting a distribution of light for activedepth sensing or for flood illumination), the uneven surfaces 908 and910 may be oriented in the same direction. FIG. 9C is a depiction 960 oftwo DOEs 902 and 904 with the material 906 in between and the unevensurfaces 908 and 910 oriented away from a light source (with the lighttravelling from left to right). The refractive index of the first DOE902 and the refractive index of the refractive material 906 may be thesame (e.g., the differences being less than a threshold). In thismanner, the surface 908 may seem to be non-existent to light passingthrough the first DOE 902 and the material 906. As a result, the lightis only affected by the second DOE 904 with the surface 910. FIG. 9D isa depiction 970 of the two DOEs 902 and 904 with the material 906 inbetween and the uneven surfaces 908 and 910 oriented away from a lightsource (with the light travelling from left to right). The refractiveindex of the first DOE 902 and the refractive index of the refractivematerial 906 are different (e.g., the differences being greater than athreshold). The refractive index of the second DOE 904 and therefractive index of the refractive material 906 may be the same ordifferent. In this manner, both surfaces 908 and 910 may affect thedistribution of light passing through the diffractive element.

FIG. 9E is a depiction 980 of two DOEs 902 and 904 with the material 906in between and the uneven surfaces 908 and 910 oriented toward a lightsource (with the light travelling from left to right). The refractiveindex of the second DOE 904 and the refractive index of the refractivematerial 906 are different (e.g., the differences being greater than athreshold). The refractive index of the first DOE 902 and the refractiveindex of the refractive material 906 may be different (e.g., thedifferences being greater than a threshold). In this manner, bothsurfaces 908 and 910 may affect the distribution of light passingthrough the diffractive element. FIG. 9F is a depiction 990 of the twoDOEs 902 and 904 with the material 906 in between and the unevensurfaces 908 and 910 oriented away from a light source. The refractiveindex of the second DOE 904 and the refractive index of the material 906may be the same. In this manner, the surface 910 may seem to benon-existent to light passing through the material 906 and the secondDOE 904. As a result, the distribution of light passing through thediffractive element is only affected by the first DOE 904 with thesurface 908. Other suitable arrangements and orientations of two or moreDOEs may be used, and the present disclosure should not be limited tothe examples in FIGS. 9A-9F.

In some example implementations, the projector may be configured toadjust the refractive index of the refractive material with respect tothe light passing through the diffractive element. In this manner, therefractive index of the refractive material 906 may appear to be thesame as one of the DOEs 902 or 904 in some instances or operating modesand different than the DOE 902 or 904 in other instances or operatingmodes. Through adjusting the refractive index of the refractive material906, the projector may be configured to switch between generate lightdistributions from each of the DOEs, or the projector may be configuredbetween using one DOE and using two DOEs to generate the lightdistribution.

In some example implementations, the refractive index of the refractivematerial may be based on the polarity of the light passing through thematerial. For example, a light with a first polarity may be associatedwith a first refractive index while a light with a second polarity maybe associated with a second refractive index for the refractive material906. In some example implementations, the material may be a birefringentmaterial, with the two refractive indexes being the refractive indexesof the two DOEs on either side of the material. A first refractive indexof the material may be for polarized light with light waves in a firstlinear direction. A second refractive index of the material may be forpolarized light with light waves in a second linear direction 90 degreesto the first linear direction.

FIG. 10 is a depiction 1000 of an example waveform for a first polarity1004 and an example waveform for a second polarity 1006 ninety degreesto the first polarity 1004 for light travelling in direction 1002. Thematerial having a first refractive index for the first polarity 1004 mayalter polarized light with the first polarity 1004 passing through thematerial based on the first refractive index. The material having asecond refractive index for the second polarity 1006 may alter polarizedlight with the second polarity 1006 passing through the material basedon the second refractive index.

Unpolarized light travelling along direction 1002 includes light withwaveforms in any plane on the direction 1002. For example, a portion ofthe unpolarized light has a first polarity 1004, another portion of theunpolarized light has a second polarity 1006, and other portions of theunpolarized light have polarities between the first polarity 1004 andthe second polarity 1006. Each of the portions of light can be modeledas including a first energy with a first polarity 1004 and including asecond energy with a second polarity 1006. For example, light with apolarity 45 degrees to the first polarity 1004 and the second polarity1006 may be modeled as having half of its energy with the first polarity1004 and having the other half of its energy with the second polarity1006. Other portions of the unpolarized light may be modeled similarly.For a material with the first and second refractive indexes based on thepolarity of the light, the first energy of the light may be alteredbased on the first refractive index, and the second energy of the lightmay be altered based on the second refractive index.

The DOE on either side of the birefringent material also may have arefractive index that is based on the polarity of the light passingthrough the DOE. For example, referring back to FIGS. 9A and 9B, thefirst DOE 902 may have a refractive index that is identical to the firstrefractive index of the birefringent material 906 for light of a firstpolarity 1004 (FIG. 10), and the second DOE 904 may have a refractiveindex that is identical to the second refractive index of thebirefringent material 906 for light of a second polarity 1006 (FIG. 10).The DOEs 902 and 904 may not affect or alter light with a polarityassociated with the refractive index of the material 906 that isidentical to the refractive index of the respective DOE 902 or 904. Inthis manner, if light passing through the elements 902-906 includes afirst energy with a first polarity 1004 and a second energy with asecond polarity 1006, the first energy of the light may be affected oraltered based on the surface 910 of the second DOE 904 (similar to FIG.9A, with the first DOE 902 appearing as invisible for the first energyof the light). Similarly, the second energy of the light may be affectedor altered based on the surface 908 of the first DOE 902 (similar toFIG. 9B, with the second DOE 904 appearing as invisible for the secondenergy of the light).

If the first DOE 902 distributes (or replicates) light from a lightsource (such as a laser or a laser array) into a first distribution oflight points, the second energy of the light is divided into the lightpoints of the first distribution. If the second DOE 904 distributes (orreplicates) light from a light source (such as a laser or a laser array)into a second distribution of light points, the first energy of thelight is divided into the light points of the second distribution. Thefirst distribution and the second distribution may be interleaved orotherwise combined (such as without any points between the distributionsoverlapping) to generate the final distribution for the projector. Whilethe examples use the first polarity 1004 and the second polarity 1006 inFIG. 10, any perpendicular polarities along a direction may be used, andthe example polarities are provided for ease of explanation. The presentdisclosure should not be limited to specific directions for thepolarities regarding the refractive indexes.

Unpolarized light (or polarized light 45 degrees to the first polarity1004 and the second polarity 1006) can be modeled as having half of itsenergy with the first polarity 1004 and having the other half of itsenergy with the second polarity 1006. Unpolarized light (or 45 degreepolarized light) passing through the three elements 902-906 has half ofits energy divided into the first distribution of light points (based onthe first DOE 902) and has the other half of its energy divided into thesecond distribution of light points (based on the second DOE 904) basedon the birefringent properties of the material 906. If the firstdistribution and the second distribution include the same number oflight points, each light point of the final distribution may have thesame energy as any other light point of the final distribution.Alternatively, if the number of light points differ between the firstdistribution and the second distribution, a light point from the firstdistribution may have a different energy than a light point from thesecond distribution. The difference in energy between the light pointsmay be based on the number of light points in the first distributionrelative to the number of light points in the second distribution.

FIG. 11 is a depiction 1100 of example first and second distributions1102 and 1104 combined for a combined (or final) distribution 1106.While the orientation of the DOEs 1108 and 1110 (and for the DOEs inFIGS. 12-14) are illustrated as having the uneven surfaces orientedtoward one another, any suitable orientation of the DOEs may be used.For example, the surfaces may be oriented in one direction (such as inany arrangement in FIGS. 7A-7I). The present disclosure should not belimited by the specific example in FIG. 11, or the examples in FIGS.12-14.

For light passing from left to right through the diffractive element1116, the first DOE 1108 may generate the first distribution 1102 withlight points 1112. The second DOE 1110 may generate the seconddistribution 1104 with light points 1114. The combined distribution thusmay include the light points 1112 and 1114. FIG. 11 illustrates thesecond distribution 1104 being a spatial shift of the first distribution1102. However, the distributions 1102 and 1104 may include differentnumbers or different locations of light points other than a uniformshift of the light points between distributions. Further, while FIG. 11illustrates the distributions 1102 and 1104 being interleaved in thecombined distribution 1106, the distributions may be combined in otherways, such as being stacked, tiled, or otherwise non-interleaved.

If the overall diffractive element 1116 is configurable, a projector maybe able to switch between projecting the distributions 1102-1106 fordifferent operating modes. In one example, the projector may beconfigured to switch between projecting the first distribution 1102 andprojecting the combined distribution 1106. In another example, if thesecond distribution 1104 includes a greater number of light points 1114than the number of light points 1112 of the first distribution 1102, theprojector may be able to switch between projecting the firstdistribution 1102, projecting the second distribution 1104, andprojecting the final distribution 1106. In this manner, a projector mayproject fewer light points for scenes with more ambient light (such asoutdoors during a sunny day) and may project more light points forscenes with less ambient light (such as indoors or night time). Theprojector may switch between which distributions of light are to beprojected by adjusting the refractive indexes for the diffractiveelement 1116 in relation to the light passing through the diffractiveelement 1116.

In some example implementations, the refractive indexes for thediffractive element 1116 may be adjustable by adjusting the polarity ofthe light passing through the element 1116. For example, referring toFIG. 10, the polarity of the light passing through the element 1116 maybe adjusted between a first polarity 1004, a second polarity 1006,and/or a polarity between the first polarity 1004 and the secondpolarity 1006. In some other example implementations, the refractiveindexes for the element 1116 may be adjusted by adjusting the physicalproperties (and thus the refractive index) of the refractive material1118. By adjusting the physical properties of the refractive material1118, the distribution of light may be adjusted regardless whether thelight passing through the diffractive element 1116 is polarized. Forexample, a distribution of unpolarized light may be adjusted based onadjusting the refractive index of the refractive material 1118.

Combining a DOE for generating a distribution of light points and adiffusion element for flood illumination may be similar to the examplein FIG. 11. FIG. 12 is a depiction 1200 of an example distribution 1202and a flood illumination 1204 that may be projected by a configurablediffractive element 1216. The DOE 1208 may project the distribution 1202with light points 1212. The diffusion element 1210 may project a floodillumination 1204 with a diffusion 1214. In one example, the refractiveindexes for the diffractive element 1216 may be adjustable to switchbetween projecting the distribution 1202 and the combined projection1206. The combined projection may include a sufficient diffusion of thelight for flood illumination. In another example, the refractive indexesfor the element 1216 may be adjustable to switch between projecting thedistribution 1202 and the flood illumination 1204. In some exampleimplementations, the refractive indexes of the material 1218 may beadjustable, or the polarity of the light passing through the element1216 may be adjustable. While the example in FIG. 12 illustrates thediffusion element 1210 after the DOE 1208 (with light travelling fromleft to right), the ordering of the elements 1208 and 1210 may beswitched. Further, while the uneven surfaces of the elements areillustrated as oriented toward each other, the surfaces may be orientedin one direction (such as in any arrangement in FIGS. 7A-7I). Thepresent disclosure should not be limited by the specific example in FIG.12.

Referring back to the diffractive element 1116 in FIG. 11, and similarfor the element 1216 in FIG. 12, the refractive indexes of the material1118 may be adjusted when electricity is applied to the material 1118.For example, when no electricity is applied, the material 1118 may be abirefringent material with a first refractive index for light with afirst polarity 1004 and a second refractive index for light with asecond polarity 1006 (FIG. 10). The first refractive index may be therefractive index of a first DOE 1108. The second refractive index may bethe refractive index of the second DOE 1110. When electricity is appliedto the material 1118, the refractive index may be exclusively the secondrefractive index for light with the second polarity. In this manner,when the light is unpolarized or having a polarity between the firstpolarity 1004 and the second polarity 1006, the projector may projectthe first distribution 1102 when electricity is applied to the material1118, and the projector may project the combined distribution 1106 whenno electricity is applied to the material 1118.

The refractive material may be coupled to one or more electricalcontacts for applying electricity to the refractive material. In someexamples of the element 1116 configured to apply electricity to thematerial 1118, the two DOEs 1108 and 1110 may be fabricated on twosubstrates. A layer of transparent electrode film (e.g., indium tinoxide) may be deposited on each substrate. The film thus may conductelectricity and apply the electricity to the material 1118.

An example material 1118 is a liquid crystal (LC). The LC includes aplurality of molecules with one or more orientations, and theorientation of the molecules affects the refractive index of the LC. Inthis manner, the refractive index of an LC may be configured byorienting the molecules of the LC. For example, if the orientation ofthe molecules are perpendicular to the LC (or the DOE surfaces), therefractive index of the LC may be one refractive index. The moleculesmay be oriented perpendicular to the LC by applying an electricity tothe LC (such as via one or more electrical contacts). If no electricityis applied, the molecules may shift to different orientations. For somebirefringent LCs, the molecules may be oriented in one of twoorientations when no electricity is applied. In this manner, the portionof the light energy with the corresponding first polarity 1004 for themolecules in the first orientation is adjusted based on the firstrefractive index, and the remainder of the light energy with thecorresponding second polarity 1006 for the molecules in the secondorientation is adjusted based on the second refractive index. For someother birefringent LCs, the molecules may be in a first orientation whenno electricity is applied and in a second orientation when electricityis applied. For some further birefringent LCs, the molecules may berandomly oriented with an average or overall refractive index of the LCas a result of the orientations of the molecules. The average refractiveindex may be the first refractive index or the second refractive indexof the DOEs on either side of the LC. In manufacturing the diffractiveelement 1116 (FIG. 11) or 1216 (FIG. 12) where the refractive materialis an LC, the molecules of the LC may be aligned and oriented in anysuitable manner so that the refractive indexes may be adjusted based onapplying an electricity to the refractive material or adjusting thepolarity of the light passing through the diffractive element 1116 or1216. If the polarity of the light is adjusted, an electricity may notbe applied to the LC. In this manner, the refractive indexes of the LCchanges with the change of the light polarization throughout operationof the light projector (and thus the light distribution is based on thepolarity of the light passing through the elements).

In applying an electricity to the refractive material between the DOEs,the projector may be similar to the projector 200 in FIG. 2 or to theprojector 300 in FIG. 3, other than the DOE 208 or 308 being replacedwith a diffractive element having multiple DOEs and a refractivematerial (such as an LC) in between (as described above). Thediffractive element may be adjusted by applying electricity to therefractive material via one or more electrical contacts (such as via anindium tin oxide layer).

FIG. 13A is a depiction of an example projector 1300 configured to applyan electricity to the LC 1314 (or other suitable refractive material) ofthe diffractive element 1304 to adjust the orientation of molecules inthe LC 1314. The projector 1300 may include a light source 1302 (such asa VCSEL, DFB laser, or an array of VCSELs or DFB lasers). The lightsource 1302 may be configured to project light 1306 toward a lens 1308,and the lens 1308 may be configured to direct the light 1306 to thediffractive element 1304 to project the projection 1318. Examplediffractive elements are as described above. In some exampleimplementations, the diffractive element 1304 includes a first DOE 1310at a proximal end of the diffractive element 1304 (relative to theincoming light 1306), a second DOE 1312 at a distal end of thediffractive element 1304 (relative to the incoming light 1306), and anLC 1314 between the first DOE 1310 and the second DOE 1312. The firstDOE 1310 and the second DOE 1312 may be a combination of a first elementto project a first distribution of light points and a second element toproject a second distribution of light points. Alternatively, the firstDOE 1310 and the second DOE 1312 may be a combination of a first elementto project a distribution of light points and a second element toproject a diffuse light. The diffractive element 1304 also may include aconductive material 1316 as one or more electrical contacts for applyingelectricity to the LC 1314 to adjust the orientation of the molecules inthe LC 1314 (thus adjusting the distribution of light of the projection1318).

First molecule orientation 1320 is illustrated as the molecules beingperpendicular to the LC 1314 and the DOEs 1310 and 1312. The firstmolecule orientation 1320 may be the orientation of molecules in the LC1314 when an electricity is applied to the LC 1314. In this manner, therefractive index of the LC 1314 may be the same as the refractive indexof the first DOE 1310 (or, alternatively, the refractive index of thesecond DOE 1312). Light passing through the diffractive element 1304thus may not be altered by the first DOE 1310 (or, alternatively, thesecond DOE 1312).

Second molecule orientation 1322 is illustrated as the molecules beingparallel to the LC 1314 and the DOEs 1310 and 1312. The second moleculeorientation 1322 may be the orientation of molecules in the LC 1314 whenno electricity is applied to the LC 1314. In this manner, the refractiveindex of the LC 1314 may be the same as the refractive index of theother DOE than for the first molecule orientation 1320. Light passingthrough the diffractive element 1304 thus may not be altered by theother DOE than for the first molecule orientation 1320.

Third molecule orientation 1324 is illustrated as the molecules randomlyoriented. The third molecule orientation 1324 is another exampleorientation of molecules in the LC 1314 when no electricity is appliedto the LC 1314. The LC 1314 with the third molecule orientation 1324 maybe configured to have an average refractive index that is different thanthe refractive index of the first DOE 1310 and that is different thanthe refractive index of the second DOE 1312 (e.g., the differences beinggreater than a threshold). The average refractive index for the LC 1314with the third molecule orientation 1324 may be an average of (i) therefractive index of the LC 1314 with the first molecule orientation 1320and (ii) the refractive index of the LC 1314 with the second moleculeorientation 1322. In this manner, all of the light passing through thediffractive element 1304 experiences the same refractive index that isdifferent from the first DOE 1310 and the second DOE 1312. As a result,all of the light passing through the diffractive element 1304 is firstaltered by the first DOE 1310, and then altered by the second DOE 1312.

Fourth molecule orientation 1326 is illustrated as some of the moleculesoriented as in the orientation 1320 and the other molecules oriented asin the orientation 1322 when an electricity is applied to the LC 1314.The electricity may not cause some of the molecules near the surface ofthe LC or DOE to orient to a first molecule orientation (such asperpendicular to the LC or DOE surface). However, the molecules thatremain in the second molecule orientation (such as parallel to the LC orDOE surfaces) may be a thin layer relative to the feature size of theDOE. For example, the magnitudes of the peaks and valleys of the DOEsurface may be multiples of the magnitude of the layer thickness ofmolecules not changing their orientation. The LC 1314 may affect a smallportion of the light based on the parallel orientation of somemolecules, and the LC 1314 may affect the large remainder of the lightbased on the perpendicular orientation of the remaining molecules (suchas similar to the first molecule orientation 1320).

In some examples of manufacturing the LC 1314 so that the molecules maybe oriented in a specific direction (such as for orientations 1322),orientating the molecules may be difficult near the surfaces of the DOEs1310 and 1312. For example, the molecules' orientation in the creases ofthe DOE surfaces may be slightly misaligned. Use of a random orientationof molecules allows for the LC 1314 to be filled in between the firstDOE 1310 and the second DOE 1312 without concern for the orientation ofthe molecules (simplifying the manufacturing process). However, anysuitable methods for manufacturing the LC 1314 may be used, and thepresent disclosure should not be limited to a random moleculeorientation when no electricity is applied to the LC 1314 or any otherdescribed molecule orientations when no electricity is applied to the LC1314. Further, the present disclosure should not be limited to aspecific molecule orientation when an electricity is applied to the LC1314. In some example implementations, one or both of the unevensurfaces of the DOEs 1310 and 1312 may be oriented away from the LC1314, alleviating issues in attempting to orient the molecules along theuneven surfaces. Each of the example configurations in FIG. 9 may beapplied to the diffractive element 1304 in FIG. 13A.

Applying and removing an electricity to and from the LC 1314 mayconfigure the molecule orientation between the first moleculeorientation 1320 for a first mode and one of the molecule orientations1322-1326 for a second mode. In this manner, the projector 1300 mayswitch between using one of the DOEs 1310 and 1312 and using both DOEs1310 and 1312 for the projection 1318 (such as when switching themolecule orientation between orientation 1320 and orientation 1324 or1326), or the projector 1300 may switch between using a first DOE 1310and using a second DOE 1312 for the projection 1318 (such as whenswitching the molecule orientation between orientation 1320 andorientation 1322).

FIG. 13A depicts that the conductive material 1316 may be connected toor embedded in the LC 1314 (or suitable refractive material) in couplingthe conductive material 1316 to the LC 1314. In some other exampleimplementations, the conductive material 1316 may be embedded in orconnected to one or more of the DOEs in coupling the conductive material1316 to the LC 1314 for applying electricity to the LC 1314.

FIG. 13B is another depiction of the example projector 1300 with adifferent example location of the conductive material 1316 for applyingelectricity to the LC 1314. One or more conductive materials 1316 may beembedded in the first DOE 1310, and one or more conductive materials1316 may be embedded in the second DOE 1312. Electricity may passbetween the conductive materials 1316 embedded in the DOEs 1310 and 1312and pass through the LC 1314.

In some example implementations, the conductive material 1316 isembedded in a DOE during DOE fabrication. For example, a DOE may befabricated on a glass substrate. To fabricate the DOE on a glasssubstrate and include the conductive material, a transparent electrodefilm may be deposited on the glass substrate. The electrode film may bemade from indium tin oxide (ITO) or any other suitable conductivematerial. The surface of the DOE may be fabricated by depositing apolymer layer on the electrode film and embossing or curing the polymer.In another example, the surface of the DOE may be fabricated bydepositing a dielectric film on the electrode film and etching thedielectric film. In this manner, the conductive material may be embeddedin the DOE and configured to apply electricity to the LC bordering theDOE surface.

FIG. 13C is another depiction of the example projector in FIG. 13A witha different example location of the conductive material 1316 forapplying electricity to the LC 1314. One or more conductive materials1316 may be disposed on the surface of the first DOE 1310, and one ormore conductive materials 1316 may be disposed on the surface of thesecond DOE 1312. Electricity may pass between the conductive materials1316 disposed on the surfaces of the DOEs 1310 and 1312 to pass throughthe LC 1314. The conductive material 1316 may be a transparent electrodefilm (such as made from ITO or another suitable material) placed on thesurface of the DOE during or after DOE fabrication.

While one piece of conductive material per DOE is illustrated, anynumber of conductive materials and any suitable type of conductivematerials may be used. As such, the present disclosure should not belimited to the above examples regarding the conductive materialselectrically coupled to the refractive material.

Using electricity to adjust the refractive indexes of the LC 1314 may befor unpolarized light passing through the diffractive element 1304. Forexample, a VCSEL or VCSEL array may emit unpolarized light, and thedistribution of the light of the projection 1318 may be adjusted byapplying electricity to the LC 1314 instead of polarizing the light andadjusting the polarity. Alternative to adjusting the refractive index ofthe LC 1314 by applying electricity, the refractive index of the LC maybe adjusted by adjusting the polarity of the light passing through thediffractive element. In some example implementations, DFB lasers of alight source emit polarized light, or VCSEL(s) of a light source may becoupled to or include a polarizer so that the emitted light ispolarized.

In adjusting the refractive index of the diffractive element byadjusting the polarity of the light passing through the element, aprojector may transmit linearly polarized light through the element, anda polarization rotator may be used to rotate the linear polarization ofthe light. For example, a half-wave plate may be rotated between 0 and90 degrees to adjust the polarization of the polarized light between afirst polarization 1004 and a second polarization 1006 (as illustratedin FIG. 10).

FIG. 14 is a depiction of an example projector 1400 configured to adjustthe polarity of the light passing through a diffractive element 1404 toadjust the distribution of light of the projection 1422. For example,the projector 1400 may adjust the light distribution of the projection1422 from a first distribution of light points to a second distributionof light points (and/or a third distribution of light points), or theprojector 1400 may adjust the projection 1422 from a distribution oflight points for active light depth sensing to a diffuse light for floodillumination.

The projector 1400 may include a light source 1402. Some exampleimplementations of the light source 1402 are a single laser (such as aVCSEL of DFB laser) or an array of lasers (such as a VCSEL array or aDFB laser array). The light source 1402 may be configured to emit light1406 toward the lens 1412. If the light 1406 is unpolarized (such asprovided by a VCSEL or VCSEL array), the projector 1400 optionally mayinclude a polarizer 1408 to filter the light 1406 to polarized light1410 with a first polarity. The polarity may be a linear polarity. Inthe example, the first polarity is described as the first polarity 1004(FIG. 10) for ease of explanation, but any suitable polarity may beused.

The lens 1412 may be configured to direct the polarized light 1410toward the diffractive element 1404. The diffractive element 1404 may besimilar to the diffractive element 1304 in FIGS. 13A-13C, other than anelectricity may not be applied to the LC 1424 in adjusting theorientation of the molecules in the LC 1424. For example, thediffractive element 1404 may not include the conductive material (suchas transparent conductive electrodes embedded in the DOEs). In someexample implementations, the orientation of the molecules is the secondmolecule orientation 1322 (FIG. 13).

The projector 1400 further may include a polarity rotator 1414 forrotating the polarity of the polarized light 1410. For example, thepolarity rotator 1414 may be a filter configured to rotate the polarityof the polarized light 1410 anywhere from the first polarity 1004 to thesecond polarity 1006. In some example implementations, the polarityrotator 1414 is a half-wave plate. The half-wave plate may be an LCwaveplate configured for adjusting the polarity of the light by rotatingbetween 0 degrees (such as for the first polarity 1004) and 45 degrees(such as for the second polarity 1006 90 degrees to the first polarity1004). However, any suitable component for rotating or adjusting thepolarity of the light 1410 may be used.

For the diffractive element 1404, the first DOE 1418 may have a firstrefractive index, and the second DOE 1420 may have a second refractiveindex. The LC 1424 may be birefringent with the first refractive index(of the first DOE 1418) for light with a first polarity 1004 and thesecond refractive index (of the second DOE 1420) for light with a secondpolarity 1006. In this manner, the projection 1422 may be adjusted basedon the polarity of the polarized light 1416. Any of the orientations ofthe DOEs in FIGS. 9A-9F, or any other suitable orientation of the DOEs,may be applied to the diffractive element 1404 in FIG. 14.

FIG. 15 is a depiction 1500 of example adjustments to the polarity ofthe light by adjusting the orientation of the polarity rotator 1502. Theexamples illustrate a half-wave plate as the polarity rotator 1502 inadjusting the polarity, but any suitable component may be used. In someexamples, light with a first polarity 1004 (as illustrated in FIG. 10)may remain at a first polarity 1004 when the polarity rotator 1502 has a0 degree rotation 1504. Light with a first polarity 1004 may be changedto a second polarity 1006 when the polarity rotator 1502 has a 45 degreerotation 1506. Light with a first polarity 1004 may be changed to athird polarity 1510 (between the first polarity 1004 and the secondpolarity 1006) when the polarity rotator 1502 has a rotation 1508between 0 degrees and 45 degrees. Light with a third polarity 1510 thusmay have a first component with a first polarity 1004 and a secondcomponent with a second polarity 1006.

FIG. 16A is a depiction 1600 of the projections based on the polarity oflight passing through the diffractive element 1404. For light having afirst polarity 1004, the first DOE of the diffractive element 1404 maydivide the light into the projection 1602 (with the second DOE having noimpact on the distribution of light). For light having a second polarity1006, the second DOE of the diffractive element 1404 may divide thelight into the projection 1604. The projection 1604 may have more orless light points than the projection 1602. In this manner, theprojector 1400 (FIG. 14) may adjust the density of the distribution oflight points by rotating the polarity of the light by 90 degrees.

For light having a third polarity 1510 between the first polarity 1004and the second polarity 1006, each DOE of the diffractive element 1404may divide a portion of the light into the projection 1602 and theprojection 1604 combined to generate the projection 1606 (based on therefractive indexes of the LC 1424). If the projection 1604 includes moreor less light points than the projection 1602, the angle of the thirdpolarity 1510 may be based on the number of light points of theprojection 1604 relative to the number of light points of the projection1602 so that each light point in the projection 1606 has the sameenergy. For example, if the projection 1604 includes twice as many lightpoints as the projection 1602, the energy is dispersed twice as much forthe projection 1604 than the projection 1602. As a result, the thirdpolarity 1510 may be at 54.7 degrees relative to the first polarity 1004at 0 degrees so that twice as much energy is to be dispersed for theprojection 1604 than for the projection 1602. If the projection 1604 hasthe same number of light points as the projection 1602, the light energymay be divided equally between the first polarity 1004 and the secondpolarity 1006, and the third polarity 1510 may be at 45 degrees relativeto the first polarity 1004 at 0 degrees. While FIG. 16A is depictedregarding adjusting the density of a distribution of light points, thesame may apply for switching between a distribution of light points foractive light depth sensing and a diffuse light for flood illumination.

FIG. 16B is a depiction 1650 of projections including a distribution oflight points or flood illumination based on the polarity of lightpassing through the diffractive element 1404. For light having a firstpolarity 1004, the first DOE of the diffractive element 1404 may dividethe light into the projection 1612 (with the second DOE (diffusionelement) having no impact). For light having a second polarity 1006, thesecond DOE (diffusion element) of the diffractive element 1404 maydiffuse the light for flood illumination, such as illustrated by theprojection 1614. In this manner, the projector 1400 (FIG. 14) may switchbetween projecting a distribution of light points and flood illuminationby rotating the polarity of the light 90 degrees.

With a projector configured to adjust its projection (such as adjustingthe density of the distribution of light points or switching betweenprojecting a distribution of light points and flood illumination), adevice including the projector may be configured to control operation ofthe projector. For example, the device 600 (FIG. 6) may be configured tocontrol operation of the transmitter 601, including adjusting thedistribution of light from the transmitter 601. The distribution oflight may be adjusted by adjusting the refractive indexes of adiffractive element in the transmitter 601 (such as through applying anelectricity to a birefringent refractive material, such as an LC, orthrough adjusting the polarity of the light passing through thediffractive element).

FIG. 17 is an illustrative flow chart depicting an example operation1700 for adjusting the distribution of light to be projected by aprojector. The device 600 in FIG. 6 is referred to in performing theexample operation 1700 for ease of explanation, but any suitable devicemay perform the example operation 1700. Further, operations forcontrolling the transmitter 601 may be performed by the light controller610 (such as the signal processor 612), the processor 604, and/or anyother suitable component of the device 600.

Beginning at 1702, the device 600 may determine whether the transmitter601 is to project a first projection or a second projection. In someaspects, the first projection may be a first distribution of light foractive depth sensing, and the second projections may be a diffuse lightfor flood illumination. In some other aspects, the first projection maybe a first distribution of light, and the second projection may be asecond distribution of light different from the first distribution.Other suitable combinations of projections may exist, and the presentdisclosure should not be limited to the provided examples.

In some example implementations, the determination of which projectionis to be projected may be based on whether flood illumination or activedepth sensing is to be performed by the device 600 (1704). In some otherexample implementations where active depth sensing is to be performed,the device 600 may determine a suitable distribution density of light(1706) where the first projection and the second projection includedifferent density distributions (e.g., as illustrated in FIG. 11). Thedetermination may be based on the amount of ambient light existing inthe scene. Additionally or alternatively, the determination may be basedon the resolution needed, the application for which active depth sensingis to be performed, or the distance of the object from the device 600for which active depth sensing is being performed. For example, facialrecognition applications may require a higher resolution (and thus ahigher density of light distribution by the transmitter 601) than objecttracking or range finding applications.

While not illustrated, the device 600 may determine whether a thirdprojection is to be projected. For example, the device 600 may determinewhether the transmitter 601 should project the first projection and thesecond projection as a combined projection (such as to increase thedensity of a distribution by projecting a first density distribution anda second density distribution).

If the transmitter 601 is to project the first projection (1708), thetransmitter 601 may project the first projection via a diffractiveelement with first refractive indexes (1710). The diffractive elementmay include two DOEs with a refractive material (such as a LC) inbetween, as described in the above examples. In some exampleimplementations of the diffractive element having first refractiveindexes, the transmitter 601 may transmit light through the diffractiveelement without applying an electricity to the refractive materialbetween the DOEs (1712). In some other example implementations, thetransmitter 601 may transmit polarized light through the diffractiveelement without adjusting the polarity of the light (1714). For example,the polarity of the light may remain in a first polarity 1004 whenpassing through a half-wave plate as a result of the half-wave plate ofthe projector remaining at a rotation of 0 degrees.

Referring back to 1708, if the transmitter 601 is to project the secondprojection, the device 600 may adjust the refractive indexes of thediffractive element (1716). In some example implementations, the device600 may apply an electricity to the refractive material between thefirst DOE and the second DOE of the diffractive element (1718). Forexample, an electricity may be applied to an LC to adjust theorientation of the molecules in the LC. In some other exampleimplementations, the device 600 may rotate the polarity of polarizedlight transmitted through the diffractive element (1720). For example,the device 600 may adjust a polarity rotator (such as rotating ahalf-wave plate) to rotate the polarity of the light from 0 degrees toup to 90 degrees.

The transmitter 601 then may project the second projection via thediffractive element with the adjusted refractive indexes (1722). Whilethe example operation 1700 describes projection of a first projection ora second projection, any number of projections may be projected (such asa third projection). The plurality of projections may be for floodillumination or active depth sensing, based on the DOEs of thediffractive element in the transmitter 601.

For active depth sensing, and specifically referring to a lightprojector whose projected distribution of light is adjustable based onthe polarity of the light, a device (such as device 600 in FIG. 6) maycontrol the transmitter 601 to adjust the polarity of the light from thetransmitter 601. FIG. 18 is an illustrative flow chart depicting anexample operation 1800 for adjusting the light projection from a lightprojector. The device 600 in FIG. 6 is referred to in performing theexample operation 1800 for ease of explanation, but any suitable devicemay perform the example operation 1800. Further, operations forcontrolling the transmitter 601 may be performed by the light controller610 (such as the signal processor 612), the processor 604, and/or anyother suitable component of the device 600. Additionally, thetransmitter 601 is described as including a diffractive element, such asdescribed above. However, any suitable diffractive element may be usedin performing the steps of the example operation 1800.

Beginning at 1802, the transmitter 601 may emit polarized light. In someexample implementations, a light source of the transmitter 601 may emitunpolarized light (1804). For example, the light source may be one ormore VCSELs that emit unpolarized light. The transmitter then maypolarize the emitted light (1806). For example, a polarizer may receivethe unpolarized light from the one or more VCSELs, and polarize theemitted light to have a first polarity. In some other exampleimplementations, the light source of the transmitter 601 may emitpolarized light (1808). For example, the light source may be one or moreDFB lasers to emit light having a first polarity. In this manner, apolarizer may not be needed to polarize the light from the light source.

Proceeding to 1810, the device 600 may determine whether the transmitter601 is to operate in a first mode. In some example implementations, thetransmitter 601 may switch between a first mode and a second modeassociated with projecting different distributions of light. In someother example implementations, the transmitter 601 may switch betweenthe first mode, the second mode, and a third mode associated withprojecting different distributions of light. While the examples describeswitching between two or three modes, the transmitter 601 may beconfigured to switch between any number of modes and project any numberof light distributions, and the present disclosure should not be limitedto the examples.

The first mode may be associated with a first distribution of light, andthe second mode may be associated with a second distribution of light.In some example implementations, the distributions of light may bedistributions of light points, and the first distribution of light mayhave a fewer number of light points (sparser density of light points)than the second distribution of light. In this manner, each light pointin the first distribution may have a greater intensity than each lightpoint in the second distribution. Since a fewer number of light pointsmay exist for the first distribution (when the transmitter 601 isoperating in the first mode) than for the second distribution (when thetransmitter 601 is operating in the second mode), and the intensity ofeach light point may be greater in the first distribution than in thesecond distribution, the device 600 may determine to operate thetransmitter 601 in the first mode, e.g., for performing active depthsensing when a greater level of interference exists in the scene or fordetermining depths of objects further from the device 600 than for thesecond mode.

In an example of determining whether to operate the transmitter 601 inthe first mode or in the second mode, the determination may be based onthe amount of ambient light or other interference in the scene. Forexample, the device 600 may capture an image or measure the ambientlight in a scene using the receiver 602. If the ambient light is greaterthan a threshold, the device 600 may determine to operate thetransmitter 601 in the first mode for active depth sensing. If theambient light is less than the threshold, the device 600 may determineto operate the transmitter 601 in the second mode for active depthsensing.

In another example, the determination as to which mode to operate thetransmitter 601 may be based on an application being executed by thedevice 600. For example, if the device 600 is performing facialrecognition, a greater number of light points for the light distributionmay be beneficial, and the device 600 may determine to operate thetransmitter 601 in the second mode. In one example, facial recognitionmay be used for payment approval by or unlocking of mobile paymentapplications. Such applications are typically executed indoors with lessinterference from ambient light than outdoors. As a result, theinterference may not be substantial enough for a greater number of lightpoints with each point having less intensity to cause problems for thefacial recognition. If the device 600 is performing facial recognitionto open the phone outdoors (which may have more interference fromambient light than indoors), or range finding of objects greater than athreshold distance from the device 600, stronger intensity light pointsmay be beneficial, and the device 600 may determine to operate thetransmitter 601 in the first mode.

In some example implementations where the transmitter 601 may operate ina third mode associated with a third distribution of light, the thirddistribution of light may have more points of light than the firstdistribution of light and the second distribution of light. For example,the third distribution of light may be a combination of the firstdistribution of light and the second distribution of light. In someexamples, the third distribution of light may have a number of lightpoints equal to the summation of the number of light points of the firstdistribution of light and of the second distribution of light. In thismanner, the intensity of each light point in the third distribution oflight may be less than the intensity of each light point in the firstdistribution of light and in the second distribution of light. Thedevice 600 may determine in which mode to operate the transmitter 601based on, e.g., the resolution required by an application and/or theamount of ambient light or other interference existing in the scene. Forexample, the device 600 may determine to operate the transmitter 601 inthe third mode if the ambient light or interference is below a thresholdin order to have a higher resolution for active depth sensing than ifoperating in the first mode or the second mode.

Referring back to 1810, if the device 600 determines that thetransmitter 601 is to operate in the first mode, a diffractive elementof the transmitter 601 may project a first distribution of light fromthe emitted light based on the emitted light having a first polarity(1812). The diffractive element may include a first DOE and a second DOE(such as described above or illustrated in FIG. 14). In some exampleimplementations of the transmitter 601 operating in the first mode, thefirst DOE may project the first distribution of light (1814), and thesecond DOE may be prevented from projecting the second distribution oflight (1816) based on the emitted light having a first polarity.Referring back to 1810, if the device 600 determines that thetransmitter 601 is not to operate in the first mode (such as to operatein a second mode), the diffractive element of the transmitter 601 mayproject a second distribution of light from the emitted light based onthe emitted light having a second polarity (1818).

In some example implementations, the first DOE has a first refractiveindex associated with a first polarity, the second DOE has a secondrefractive index associated with a second polarity, and the diffractiveelement also includes a birefringent material between the first DOE andthe second DOE having the first refractive index and the secondrefractive index. In this manner, if the polarity of the emitted lightis adjusted to and from the first polarity, the device 600 may adjustpreventing and enabling the second DOE from projecting the seconddistribution of light. If the second polarity is 90 degrees relative tothe first polarity, and the polarity of the emitted light is adjusted toand from the second polarity, the device 600 may adjust preventing andenabling the first DOE from projecting the first distribution of light.

In some example implementations, a second mode may be associated withthe polarity of the emitted light being between the first polarity andthe second polarity. In this manner, the distribution of light from thediffractive element may be a combination of the first distribution oflight (projected by the first DOE) and the second distribution of light(projected by the second DOE). In some examples, the transmitter 601 mayadjust (such as rotate) the polarity of the emitted light between thefirst polarity and the second polarity (1820). For example, a polarityrotator (such as a half-wave plate) may be rotated less than 45 degreesto adjust the polarity of the emitted light to between the firstpolarity and the second polarity. The diffractive element of thetransmitter 601 then may project a combination of the first distributionof light and the second distribution of light (1822) based on theadjusted polarity of the emitted light.

In some other example implementations, a second mode may be associatedwith the polarity of the emitted light being the second polarity (90degrees relative to the first polarity). In this manner, thedistribution of light from the diffractive element may be the seconddistribution of light (projected by the second DOE), and the first DOEmay be prevented from projecting the first distribution of light. Insome examples, the transmitter 601 may adjust (such as rotate) thepolarity of the emitted light 90 degrees from the first polarity to thesecond polarity (1824). For example, a polarity rotator (such as ahalf-wave plate) may be rotated 45 degrees to adjust the polarity of theemitted light. The second DOE of the diffractive element of thetransmitter 601 then may project the second distribution of light(1826), and the first DOE may be prevented from projecting the firstdistribution of light based on the adjusted polarity of the emittedlight (1828).

While not shown, if the second mode is associated with the secondpolarity for the emitted light 90 degrees relative to the firstpolarity, a third mode may exist for the transmitter 601 and beassociated with a third polarity for the emitted light between the firstpolarity and the second polarity. In this manner, the transmitter 601may project a combination of the first distribution of light and thesecond distribution of light when operating in the third mode (similarto steps 1820 and 1822 described above).

Referring back to steps 1812 and 1818, the example operation may revertto decision 1810. In this manner, the device 600 periodically maydetermine whether to switch operating modes for the transmitter 601(such as between a first mode and a second mode, and optionally, a thirdmode). In one example, the device 600 may determine if the amount ofambient light increases above or decreases below the threshold indetermining when to switch between operating modes. In another example,the device 600 may determine a change in application being executed, achange in use case for active depth sensing, or other suitable criteriafor switching modes of the transmitter 601. In response to determiningthat the transmitter 601 is to switch operating modes, the device 600may instruct the transmitter 601 to adjust the polarity of the emittedlight passing through the diffractive element (such as by rotating ahalf-wave plate to rotate the polarity of the emitted light). In thismanner, a single light projector may be adjusted for projectingdifferent distributions of light for active depth sensing.

The techniques described herein may be implemented in hardware,software, firmware, or any combination thereof, unless specificallydescribed as being implemented in a specific manner. Any featuresdescribed as modules or components may also be implemented together inan integrated logic device or separately as discrete but interoperablelogic devices. If implemented in software, the techniques may berealized at least in part by a non-transitory processor-readable storagemedium (such as the memory 606 in the example device 600 of FIG. 6)comprising instructions 608 that, when executed by the processor 604 (orthe controller 610 or the signal processor 612), cause the device 600 toperform one or more of the methods described above. The non-transitoryprocessor-readable data storage medium may form part of a computerprogram product, which may include packaging materials.

The non-transitory processor-readable storage medium may comprise randomaccess memory (RAM) such as synchronous dynamic random access memory(SDRAM), read only memory (ROM), non-volatile random access memory(NVRAM), electrically erasable programmable read-only memory (EEPROM),FLASH memory, other known storage media, and the like. The techniquesadditionally, or alternatively, may be realized at least in part by aprocessor-readable communication medium that carries or communicatescode in the form of instructions or data structures and that can beaccessed, read, and/or executed by a computer or other processor.

The various illustrative logical blocks, modules, circuits andinstructions described in connection with the embodiments disclosedherein may be executed by one or more processors, such as the processor604 or the signal processor 612 in the example device 600 of FIG. 6.Such processor(s) may include but are not limited to one or more digitalsignal processors (DSPs), general purpose microprocessors, applicationspecific integrated circuits (ASICs), application specific instructionset processors (ASIPs), field programmable gate arrays (FPGAs), or otherequivalent integrated or discrete logic circuitry. The term “processor,”as used herein may refer to any of the foregoing structures or any otherstructure suitable for implementation of the techniques describedherein. In addition, in some aspects, the functionality described hereinmay be provided within dedicated software modules or hardware modulesconfigured as described herein. Also, the techniques could be fullyimplemented in one or more circuits or logic elements. A general purposeprocessor may be a microprocessor, but in the alternative, the processormay be any conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

While the present disclosure shows illustrative aspects, it should benoted that various changes and modifications could be made hereinwithout departing from the scope of the appended claims. For example,while the projectors are illustrated as including a lens to direct lighttoward a diffractive element, a projector may not include a lens or mayinclude multiple lenses. In another example, while two elements of adiffractive element are described (such as two DOEs for different lightdistributions), any number of DOEs and/or diffusion elements may existin the diffractive element, and multiple refractive materials may existin the diffractive element. In another example, the electricity appliedby the device or light projector in adjusting the projection may bealternating current (AC) or direct current (DC), and the voltage may beconstant or non-constant. The electricity therefore may be any suitableelectricity for adjusting the projection. Additionally, the functions,steps or actions of the method claims in accordance with aspectsdescribed herein need not be performed in any particular order unlessexpressly stated otherwise. For example, the steps of the describedexample operations, if performed by the device 600, the controller 610,the processor 604, and/or the signal processor 612, may be performed inany order and at any frequency. Furthermore, although elements may bedescribed or claimed in the singular, the plural is contemplated unlesslimitation to the singular is explicitly stated. Accordingly, thedisclosure is not limited to the illustrated examples and any means forperforming the functionality described herein are included in aspects ofthe disclosure.

What is claimed is:
 1. A device comprising a light projector, the lightprojector comprising: a light source configured to emit a light that ispolarized; a polarity rotator configured to set a polarity of theemitted light to a first polarity when the light projector is in a firstmode and to set the polarity of the emitted light to a second polaritywhen the light projector is in a second mode; and a diffractive elementconfigured to: receive the emitted light; project a first distributionof light when the received light has the first polarity, the firstdistribution of light having a first density of projected light points;and project a second distribution of light when the received light hasthe second polarity, the second distribution of light having a seconddensity of projected light points that is different than the firstdensity of projected light points.
 2. The device of claim 1, wherein thediffractive element comprises: a first diffractive optical elementconfigured to project the first distribution of light in the first mode;and a second diffractive optical element configured to project thesecond distribution of light in the second mode.
 3. The device of claim2, wherein the diffractive element further comprises a birefringentmaterial between the first diffractive optical element and the seconddiffractive optical element, wherein: the first diffractive opticalelement has a first refractive index; the second diffractive opticalelement has a second refractive index; and the birefringent material hasthe first refractive index and the second refractive index.
 4. Thedevice of claim 3, wherein the diffractive element is further configuredto project a combination of the first distribution of light projected bythe first diffractive optical element and the second distribution oflight projected by the second diffractive optical element during thesecond mode.
 5. The device of claim 4, wherein the polarity rotator isconfigured to rotate 45 degrees in switching the light projector betweenthe first mode and the second mode.
 6. The device of claim 3, whereinthe diffractive element is further configured to prevent the firstdiffractive optical element from projecting the first distribution oflight during the second mode.
 7. The device of claim 6, wherein thepolarity rotator is configured to rotate 90 degrees in switching thelight projector between the first mode and the second mode.
 8. Thedevice of claim 7, wherein: the diffractive element is furtherconfigured to project a third distribution of light when the receivedlight has a third polarity that is offset relative to the first polarityand the second polarity for the light projector operating in a thirdmode, wherein the third distribution of light is a combination of thefirst distribution of light projected by the first diffractive opticalelement and the second distribution of light projected by the seconddiffractive optical element; and the polarity rotator is furtherconfigured to rotate in switching the light projector between the firstmode and the third mode or between the second mode and the third mode.9. The device of claim 3, wherein the light projector further comprisesa polarizer located between the light source and the diffractiveelement, wherein: the light source includes one or more vertical cavitysurface-emitting lasers configured to emit unpolarized light; and thepolarizer is configured to polarize the emitted light with the firstpolarity.
 10. The device of claim 3, wherein the light source includesone or more distributed feedback lasers configured to emit polarizedlight having the first polarity.
 11. The device of claim 1, wherein thelight source is configured to emit infrared light, the device furthercomprising an infrared receiver configured to receive reflections of theinfrared light.
 12. The device of claim 11, further comprising one ormore processors configured to: determine one or more depths in a scenefrom the received reflections by the infrared receiver; and controloperation of the light projector.
 13. The device of claim 12, furthercomprising a color image sensor configured to receive visible light fromthe scene during the device capturing an image of the scene.
 14. Thedevice of claim 12, wherein the device is a wireless communicationdevice further comprising one or more transceivers configured forwireless communications.
 15. A method for active depth sensing,comprising: emitting light by a light source, the emitted light beingpolarized; setting a polarity of the emitted light to a first polaritywhen the light source is in a first mode for light projection andsetting the polarity of the emitted light to a second polarity when thelight source is in a second mode for light projection; receiving, by adiffractive element, the emitted light; projecting, by the diffractiveelement, a first distribution of light when the received light has thefirst polarity, the first distribution of light having a first densityof projected light points; and projecting, by the diffractive element, asecond distribution of light when the received light has the secondpolarity, the second distribution of light having a second density ofprojected light points that is different than the first density ofprojected light points.
 16. The method of claim 15, wherein: the firstdistribution of light is projected by a first diffractive opticalelement of the diffractive element during the first mode; and the seconddistribution of light is projected by a second diffractive opticalelement of the diffractive element during the second mode.
 17. Themethod of claim 16, further comprising switching between the first modeand the second mode, wherein the diffractive element further comprises abirefringent material between the first diffractive optical element andthe second diffractive optical element, wherein: the first diffractiveoptical element has a first refractive index; the second diffractiveoptical element has a second refractive index; and the birefringentmaterial has the first refractive index and the second refractive index.18. The method of claim 17, further comprising projecting a combinationof the first distribution of light projected by the first diffractiveoptical element and the second distribution of light projected by thesecond diffractive optical element during the second mode.
 19. Themethod of claim 18, wherein switching between the first mode and thesecond mode comprises rotating a polarity rotator 45 degrees.
 20. Themethod of claim 17, further comprising preventing the first diffractiveoptical element from projecting the first distribution of light duringthe second mode.
 21. The method of claim 20, wherein switching betweenthe first mode and the second mode comprises rotating a polarity rotator90 degrees.
 22. The method of claim 21, further comprising: projecting athird distribution of light by the diffractive element when the receivedlight has a third polarity that is offset relative to the first polarityand the second polarity for a light projector operating in a third mode,wherein the third distribution of light is a combination of the firstdistribution of light projected by the first diffractive optical elementand the second distribution of light projected by the second diffractiveoptical element; and rotating the polarity rotator in switching thelight projector between the first mode and the third mode or between thesecond mode and the third mode.
 23. The method of claim 17, furthercomprising polarizing with the first polarity the emitted light from thelight source, wherein the light source emits unpolarized light.
 24. Themethod of claim 15, wherein emitting the light by the light sourcecomprises emitting infrared light by the light source, the methodfurther comprising receiving reflections of the infrared light by aninfrared receiver.
 25. The method of claim 24, further comprisingdetermining, by one or more processors, one or more depths in a scenefrom the received reflections by the infrared receiver.
 26. The methodof claim 25, further comprising receiving visible light by a color imagesensor during capture of an image of the scene.
 27. The method of claim25, further comprising performing wireless communications via one ormore transceivers.
 28. A device, comprising: means for emitting lightthat is polarized; means for setting a polarity of the emitted light toa first polarity corresponding to a first mode for light projection andfor setting the polarity of the emitted light to a second polaritycorresponding to a second mode for light projection; means forprojecting a first distribution of light from the emitted light based onthe emitted light having the first polarity, the first distribution oflight having a first density of projected light points; and means forprojecting a second distribution of light from the emitted light basedon the emitted light having the second polarity, the second distributionof light having a second density of projected light points that isdifferent than the first density of projected light points.